Embodiments of the invention relate generally to diagnostic imaging methods and apparatus, and more particularly, to an apparatus and method of manufacturing a stacked x-ray detector assembly.
Typically, in CT imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. Generally, the x-ray source and the detector assembly are rotated about the gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors.
The detector assembly is typically made of a plurality of detector modules. Data representing the intensity of the received x-ray beam at each of the detector elements is collected across a range of gantry angles. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis that ultimately produces an image.
Conventional CT systems emit an x-ray with a polychromatic spectrum. The x-ray attenuation of each material in the subject depends on the energy of the emitted x-ray. If CT projection data is acquired at multiple x-ray energy levels or spectra, the data contains additional information about the subject or object being imaged that is not contained within a conventional CT image. For example, spectral CT data can be used to produce a new image with x-ray attenuation coefficients equivalent to a chosen monochromatic energy. Such a monochromatic image includes image data where the intensity values of the voxels are assigned as if a CT image were created by collecting projection data from the subject with a monochromatic x-ray beam. Spectral CT data facilitates better discrimination of tissues, making it easier to differentiate between materials such as tissues containing calcium and iodine, for example.
A principle objective of energy sensitive scanning is to obtain diagnostic CT images that enhance information (contrast separation, material specificity, etc.) within the image by utilizing two or more scans at different chromatic energy states. High frequency generators have made it possible to switch the kVp potential of the high frequency electromagnetic energy projection source on alternating views. As a result, data for two or more energy sensitive scans may be obtained in a temporally interleaved fashion rather than two separate scans made several seconds apart as typically occurs with previous CT technology. The interleaved projection data may furthermore be registered so that the same path lengths are defined at each energy level using, for example, some form of interpolation.
Conventional curvilinear detector array include a large number of individual detector elements arranged on the detector array. The detector elements are scintillator/photodiode cells arranged in two-dimensional modules that are then combined into two-dimensional detector area arrays. The coverage area of the detector array is defined by the number of detector elements in each 2D module and the number of 2D modules that are combined to form the detector assembly.
While known systems and methods that include conventional curvilinear detector arrays can be employed to acquire projection data at multiple x-ray energy levels or spectra and display, the coverage area of a scan is defined by the size of the detector array. Because each individual detector element has its own element-specific readout channel, the larger the detector assembly the more costly and complex the imaging system becomes.
For various imaging applications, such as cardiac scanning, it would be advantageous to acquire all of the image data for the object being imaged in a single rotation of the gantry. Such an image data acquisition technique has a number of benefits, including minimizing motion artifacts, as an example. However, the coverage area of the detector assembly must be sized based on the size of the projection of the object being imaged on the detector array. A curvilinear detector assembly designed with a large enough coverage area to image a heart, for example, would be extremely complex and cost prohibitive.
Therefore, it would be desirable to design an x-ray detector assembly that overcomes the aforementioned drawbacks.